Gas turbine engine with distributed fans

ABSTRACT

A gas generator has at least one compressor rotor, at least one gas generator turbine rotor and a combustion section. A fan drive turbine is positioned downstream of a path of the products of combustion having passed over the at least one gas generator turbine rotor. The fan drive turbine drives a shaft and the shaft engages gears to drive at least three fan rotors.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/597,510, filed Jan. 15, 2015, which claims priority to U.S.Provisional Patent Application Nos. 61/989,675, filed May 7, 2014;61/938,907, filed Feb. 12, 2014; and 61/937,153, filed Feb. 7, 2014.

BACKGROUND OF THE INVENTION

Gas turbine engines are known and typically include a fan delivering airas bypass air into a bypass housing and further delivering air into acore engine. Air in the core engine is directed into a compressor whereit is compressed. The compressed air is then delivered into a combustionsection where it is mixed with fuel and ignited. Products of thiscombustion pass downstream over turbine rotors, driving them to rotate.

Recently, it has been proposed to increase the diameter of the fan to,in turn, increase bypass ratios, or the volume of air delivered asbypass or propulsion air compared to the volume of air delivered intothe core engine. However, the ability to make this increase is somewhatlimited by the packaging envelope available on an aircraft.

It has been proposed to replace a single large diameter with a pluralityof fan rotors. However, the proposals for driving the plurality of fanrotors have deficiencies in general.

SUMMARY OF THE INVENTION

In a featured embodiment, a gas turbine engine comprises a gas generatorwith at least one compressor rotor, at least one gas generator turbinerotor and a combustion section. A fan drive turbine is positioneddownstream of a path of the products of combustion having passed overthe at least one gas generator turbine rotor. The fan drive turbinedrives a shaft and the shaft engages gears to drive at least three fanrotors.

In another embodiment according to the previous embodiment, the gasgenerator includes at least two compressor rotors and at least two gasgenerator turbine rotors. The fan drive turbine is positioned to bedownstream of a path of the products of combustion having passed overeach of the at least two gas generator turbine rotors.

In another embodiment according to any of the previous embodiments, anaxis of rotation of the gas generator is generally perpendicular to anaxis of rotation of the shaft.

In another embodiment according to any of the previous embodiments, anaxis of rotation of the gas generator is generally coaxial with an axisof rotation of the shaft.

In another embodiment according to any of the previous embodiments, theshaft is generally hollow.

In another embodiment according to any of the previous embodiments, theshaft includes at least one flex coupling associated with a gear fordriving one of the fan rotors.

In another embodiment according to any of the previous embodiments, eachfan rotor is provided with a separately driven oil pump, oil supply andoil scavenge line.

In another embodiment according to any of the previous embodiments, theat least three fan rotors include at least two distinct diameters of fanrotors.

In another embodiment according to any of the previous embodiments, eachof the at least three fan rotors have a different diameter.

In another embodiment according to any of the previous embodiments, agear ratio of the gears drive the fan rotor differs across at least twoof the fan rotors.

In another embodiment according to any of the previous embodiments, apressure ratio provided across the at least three fan rotors differsacross at least two of the fan rotors.

In another embodiment according to any of the previous embodiments, alargest diameter of the at least three fan rotors is positioned to becloser to the fan drive turbine.

In another embodiment according to any of the previous embodiments, agear ratio of the gears for driving the fan rotor differs across atleast two fan rotors.

In another embodiment according to any of the previous embodiments, ahighest gear reduction ratio is provided on the largest diameter fanrotor.

In another embodiment according to any of the previous embodiments, theshaft includes at least one flex coupling associated with a gear fordriving one of the fan rotors.

In another embodiment according to any of the previous embodiments, eachfan rotor is provided with a separately driven oil pump, oil supply andoil scavenge line.

In another embodiment according to any of the previous embodiments, apressure ratio provided across the at least three fan rotors differsacross at least two of the fan rotors.

In another embodiment according to any of the previous embodiments, theat least three fan rotors include at least two distinct diameters of fanrotors.

In another embodiment according to any of the previous embodiments, alowest fan pressure ratio is provided by a largest diameter fan rotor.

In another embodiment according to any of the previous embodiments, theshaft is generally hollow.

In another embodiment according to any of the previous embodiments,adjacent ones of the at least three fan rotors are driven to rotate inopposed directions.

These and other features may be best understood from the followingdrawings and specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a gas turbine engine.

FIG. 2 is a front view of the FIG. 1 engine.

FIG. 3 shows alternative arrangements.

FIG. 4 shows another feature.

FIG. 5 shows yet another feature.

FIG. 6 shows an option.

FIG. 7 shows another embodiment.

DETAILED DESCRIPTION

A gas turbine engine 20 is illustrated in FIG. 1 having a gas generator22. The gas generator 22 may be a two spool gas generator having a lowspeed spool in which a first upstream compressor rotor 24 driven by adownstream or low pressure turbine rotor 26. A high speed spool includesa high pressure compressor rotor 28 rotating with a high pressure orupstream turbine rotor 30. A combustion section 32 is positionedintermediate rotors 28 and 30.

An exhaust duct 34 is positioned downstream of the gas generator 22 andreceives products of combustion which have driven the turbine rotor 26to rotate. These products of combustion pass across a fan drive turbine36 mounted in a housing 37. The fan drive turbine 36 drives a shaft 38that engages a plurality of bevel gears 40 to, in turn, drive shafts 41associated with fan rotors 42, 44, 46 and 48. Each of the fan rotors 42,44, 46 and 48 are mounted within separate housings 50.

By providing a single shaft 38, which drives at least four fan rotorsand by utilizing a fan drive turbine 36 which is positioned downstreamof the last turbine rotor 26 in a gas generator 22, this disclosureprovides compact packaging, while still providing adequate drive for thefan rotors 42, 44, 46 and 48.

FIG. 2 is a front view of an aircraft wing 80, which may mount an enginesuch as engine 20. As shown, the gas generator is associated with thehousing 37. The fan rotors 42, 44, 46 and 48 have diameters that are notunduly large, such that they fit within the packaging window ofassociated wing 80.

FIG. 3 shows alternative gas generators 122 and 124. As shown, gasgenerator 122 extends to be generally parallel (actually coaxially) tothe shaft 38. Gas generator 124 extends generally vertically upwardly.Gas generators 22 and 124 rotate about an axis that is generallyperpendicular to shaft 38. Any number of other arrangements of gasgenerators relative to the shaft may be included. As can be appreciated,the fan drive turbine 36 of FIG. 1, and the fan drive turbine of theengine 12 as shown in FIG. 3 rotate on an axis this is non-parallel tothe drive axis of turbine 26. As illustrated, the fan drive turbinesrotate about an axis that is perpendicular to the drive axes of eitherengine 22 or 124.

FIG. 4 shows an alternative shaft 92 driving fan rotors 42, 44, 46 and48. This shaft 92 is hollow as shown at 94 and has flex couplings 96both upstream and downstream in a drive direction from the bevel gears40. The flexible shaft allows wing 80 to deflect, without interruptingthe drive to any one of the fan rotors.

FIG. 5 shows a further detail in which a fan rotor 110 is provided withan oil supply scavenge return line and an oil pump, shown schematicallyat 522. Given the spaced distance of the fan rotors from the gasgenerator, it would be desirable to have the oil supply incorporatedinto the fan itself rather than requiring oil lines to extend outwardlyto the fan.

FIG. 6 shows a shaft embodiment 200 wherein the gears 202 and 204associated with the shaft 201 engage bevel gears 206 and 208 to, inturn, drive fan rotors 210 and 212 in opposed directions. As shown, oneis driven counterclockwise while an adjacent one is driven clockwise.This may be beneficial if it is desired to cancel engine gyro effects.

FIG. 7 shows an engine 219 wherein the gas generator 220 delivers airacross a fan drive turbine 222 driving a shaft 300. As shown, the shaft300 drives gear 301 associated with the fan rotor 224, gear 302associated with fan rotor 226, gear 304 associated with fan rotor 228,and gear 306 associated with fan rotor 230. As can be appreciated, thediameter of the fan rotors decreases from fan rotor 224 through rotors226, 228 and 230. In addition, the fan pressure ratio may increase alongthis direction such that the fan pressure ratio of the fan rotor 224 maybe lower (1.3, for example) while the fan pressure ratio at the rotor230 may be higher (1.8, for example). In addition, a gear ratio whichreduces the speed of the fan rotors 224, 226, 228 and 230 relative toshaft 300 may decrease from the fan rotor 224 toward the fan rotor 230.As an example, the gear ratio of the gear 301 may be 1.62 while the gearratio of the gear 306 may be 0.93. In this way, the fan rotor 230 willrotate faster than the fan rotor 224.

Although various embodiments of this invention have been disclosed, aworker of ordinary skill in this art would recognize that certainmodifications would come within the scope of this invention. For thatreason, the following claims should be studied to determine the truescope and content of this invention.

The invention claimed is:
 1. A gas turbine engine comprising: a gasgenerator with at least one compressor rotor, at least one gas generatorturbine rotor and a combustion section, and there being a fan driveturbine positioned downstream of a path of products of combustion havingpassed over said at least one gas generator turbine rotor, said fandrive turbine driving a shaft and said shaft engaging gears to drive atleast three fan rotors; there being an exhaust duct downstream of saidgas generator turbine rotor, and said fan drive turbine being downstreamof said exhaust duct; and wherein a drive axis of said fan drive turbineis non-parallel to a drive axis of said at least one gas generatorturbine rotor.
 2. The gas turbine engine as set forth in claim 1,wherein said at least one compressor rotor includes at least twocompressor rotors and said at least one gas generator turbine rotorincludes at least two gas generator turbine rotors, with said fan driveturbine being positioned to be downstream of a path of the products ofcombustion having passed over each of said at least two gas generatorturbine rotors.
 3. The gas turbine engine as set forth in claim 1,wherein the drive axis of rotation of said gas generator turbine rotoris generally perpendicular to the drive axis of rotation of said fandrive turbine.
 4. The gas turbine engine as set forth in claim 1,wherein said at least three fan rotors, including at least two distinctdiameters of fan rotors.
 5. The gas turbine engine as set forth in claim4, wherein each of said at least three fan rotors have a differentdiameter.
 6. The gas turbine engine as set forth in claim 5, wherein agear ratio of said gears for driving said fan rotor differs across atleast two of said fan rotors.
 7. The gas turbine engine as set forth inclaim 6, wherein a pressure ratio provided across said at least threefan rotors differs across at least two of said fan rotors.
 8. The gasturbine engine as set forth in claim 5, wherein a largest diameter fanrotor of said at least three fan rotors is positioned to be closer tosaid fan drive turbine.
 9. The gas turbine engine as set forth in claim8, wherein a highest gear reduction ratio is provided on said largestdiameter fan rotor.
 10. The gas turbine engine as set forth in claim 1,wherein a gear ratio of said gears for driving said fan rotor differsacross at least two fan rotors.
 11. The gas turbine engine as set forthin claim 1, wherein said shaft includes at least one flex couplingassociated with one of the gears for driving one of said fan rotors. 12.The gas turbine engine as set forth in claim 1, wherein a pressure ratioprovided across said at least three fan rotors differs across at leasttwo of said fan rotors.
 13. The gas turbine engine as set forth in claim12, wherein said at least three fan rotors, including at least twodistinct diameters of fan rotors.
 14. The gas turbine engine as setforth in claim 13, wherein a lowest fan pressure ratio is provided by alargest diameter fan rotor of said at least three fan rotors.
 15. Thegas turbine engine as set forth in claim 14 wherein said shaft isgenerally hollow.
 16. The gas turbine engine as set forth in claim 1,wherein adjacent ones of said at least three fan rotors are driven torotate in opposed directions.
 17. The gas turbine engine as set forth inclaim 1, wherein said drive axis of fan drive turbine is perpendicularto a said drive axis of said at least one gas generator turbine rotor.18. A gas turbine engine comprising: a gas generator with at least onecompressor rotor, at least one gas generator turbine rotor and acombustion section, and there being a fan drive turbine positioneddownstream of a path of products of combustion having passed over saidat least one gas generator turbine rotor, said fan drive turbine drivinga shaft and said shaft engaging gears to drive at least three fanrotors; there being an exhaust duct downstream of said gas generatorturbine rotor, and said fan drive turbine being downstream of saidexhaust duct; wherein a drive axis of said fan drive turbine isnon-parallel to a drive axis of said at least one gas generator turbinerotor; wherein said shaft is generally hollow; and wherein said shaftincludes at least one flex coupling associated with one of the gears fordriving one of said fan rotors.
 19. The gas turbine engine as set forthin claim 18, wherein each of said at least three fan rotors is providedwith a separate oil pump, oil supply and oil scavenge line.
 20. A gasturbine engine comprising: a gas generator with at least one compressorrotor, at least one gas generator turbine rotor and a combustionsection, and there being a fan drive turbine positioned downstream of apath of products of combustion having passed over said at least one gasgenerator turbine rotor, said fan drive turbine driving a shaft and saidshaft engaging gears to drive at least three fan rotors; there being anexhaust duct downstream of said gas generator turbine rotor, and saidfan drive turbine being downstream of said exhaust duct; wherein a driveaxis of said fan drive turbine is non-parallel to a drive axis of saidat least one gas generator turbine rotor; and wherein each of said atleast three fan rotors is provided with a separate oil pump, oil supplyand oil scavenge line.